N-Phosphonomethylglycine, known in the agricultural chemical art as glyphosate, is a highly effective and commercially important phytotoxicant. Derivatives of N-phosphonomethylglycine described herein are also known to possess phytotoxicant activity. The present invention relates to a process for preparing glyphosate by dealkylation of a substituted ethyl moiety from the imino nitrogen of N-(substituted-ethyl)-N-phosphonomethylglycine.
It is known that amine compounds can be treated with acrylonitrile to form N-(2-cyanoethyl)-amines (Bruson, Organic Reactions, 5, 79 (1949) and Harper, Kirk-Othmer Encyclopedia of Chemical Technology, 3rd edition, 7, 370 (1979)). These substituted amines can then be decyanoethylated under several different sets of conditions. For example, heating N-cyanoethylamines as high as 180.degree. C. will give the desired amines with yields between about 28% and 61% (Butskus, Chem. Abstr., 55, 405d (1961)). These amines can also be obtained by treatment with other amines or hydroxide solution. Similar reactions are described in other publications about proteins and amino acids (Denis, Chem. Abstr., 55, 1460f (1961) and Denis, Chem. Abstr., 55, 24583 (1961)). In another reaction, sodium methoxide is employed to decyanoethylate, but this reaction is not operative in aqueous solutions (Novacek, Collections Czechoslovakian Chemical Communications, 36, 1964 (1971)). There are no literature references which describe the removal of ethyl groups having electron withdrawing moieties in the 2-position other than cyanoethyl from the nitrogen atom of an amine.